1. Field of the Invention
The present invention relates to the field of electronic packaging.
2. Prior Art
Maxim Integrated Products, Inc., through its wholly owned subsidiary, Dallas Semiconductor, has introduced the SPM product family that is a manganese lithium battery backed NVSRAM (nonvolatile static RAM). The product is unique to the industry in that the battery used to backup the SRAM is reflowable, that is, will withstand the solder reflow temperatures required for mounting onto a circuit board. Therefore the battery can be onboard the module during customer reflow. This is opposed to current systems of competitors where the battery must be attached by hand after reflow, since until recently no battery existed that could take reflow temperatures (235 C). An enclosure around the battery is required because it cannot withstand a customer water wash in its bare form. This would expose the battery to mobile ionics and eventually short the battery. For a standard eutectic reflow profile where the package is not expected to exceed 235 C, this package is qualified.
235 C is the maximum temperature requirement for reflow of lead (Pb) containing solder. However for lead free solder, exposure to a reflow temperature of 260 C may be required. For the battery package in the SPM product family, a temperature of 260 C tends to diminish the integrity of the battery enclosure, providing the opportunity of moisture intrusion over time that may cause malfunction or premature failure of the battery backup.